Thrombotic microangiopathy after renal transplantation: Current insights in de novo and recurrent disease

Effect of COVID-19 on Thrombosis Incidence and Patient Prognosis in Kidney Transplant Recipients

BACKGROUND Thrombosis poses a grave threat to patients undergoing kidney transplants, with a heightened risk of mortality. While previous studies have established a link between COVID-19 and thrombosis, the specific association between COVID-19 and thrombosis in this patient population remains unexplored. MATERIAL AND METHODS We conducted a retrospective analysis utilizing data from 394 individuals who underwent kidney transplantation within the period of September 1, 2015, to April 1, 2023. To evaluate overall survival, we employed Kaplan-Meier analysis and utilized a logistic regression model for risk analysis. Furthermore, we developed a prediction model and assessed its accuracy through calibration curves. RESULTS Out of the 394 patients included in our study, a total of 51 individuals experienced thrombosis, resulting in 2 deaths. Our analysis revealed that COVID-19 infection significantly increased the risk of thrombosis (odds ratio [OR] 8.60, 95% confidence interval 3.13-24.74, P<0.01). Additionally, the use of cyclosporine was found to elevate the risk of death (OR 20.86, 95% CI 7.93-59.24, P<0.01) according to multifactorial analysis. Logistic models were employed to screen variables, and predictive models were constructed based on the presence of COVID-19 infection and the usage of cyclosporine. A nomogram was developed, demonstrating promising accuracy in estimating the risk of thrombosis during internal validation, with a corrected C-index of 0.869. CONCLUSIONS Our study suggests that both COVID-19 infection and the use of cyclosporine can serve as reliable predictors of thrombosis risk in patients undergoing renal transplantation. Furthermore, we developed a mortality risk prediction model based on COVID-19 in assessing thrombosis.

Thrombotic microangiopathy after kidney transplantation: Expanding etiologic and pathogenetic spectra

Thrombotic microangiopathy (TMA) is an uncommon but serious complication that not only affects native kidneys but also transplanted kidneys. This review is specifically focused on post-transplant TMA (PT-TMA) involving kidney transplant recipients. Its reported prevalence in the latter population varies from 0.8% to 14% with adverse impacts on both graft and patient survival. It has many causes and associations, and the list of etiologic agents and associations is growing constantly. The pathogenesis is equally varied and a variety of patho genetic pathways lead to the development of microvascular injury as the final common pathway. PT-TMA is categorized in many ways in order to facilitate its management. Ironically, more than one causes are contributory in PT-TMA and it is often difficult to pinpoint one particular cause in an individual case. Pathologically, the hallmark lesions are endothelial cell injury and intravascular thrombi affecting the microvasculature. Early diagnosis and classification of PT-TMA are imperative for optimal outcomes but are challenging for both clinicians and pathologists. The Banff classification has addressed this issue and has developed minimum diagnostic criteria for pathologic diagnosis of PT-TMA in the first phase. Management of the condition is also challenging and still largely empirical. It varies from simple maneuvers, such as plasmapheresis, drug withdrawal or modification, or dose reduction, to lifelong complement blockade, which is very expensive. A thorough understanding of the condition is imperative for an early diagnosis and quick treatment when the treatment is potentially effective. This review aims to increase the awareness of relevant stakeholders regarding this important, potentially treatable but under-recognized cause of kidney allograft dysfunction.

The role of anticomplement therapy in the management of the kidney allograft

As the number of patients living with kidney failure grows, the need also grows for kidney transplantation, the gold standard kidney replacement therapy that provides a survival advantage. This may result in an increased rate of transplantation from HLA-mismatched donors that increases the rate of antibody-mediated rejection (AMR), which already is the leading cause of allograft failure. Plasmapheresis, intravenous immunoglobulin therapy, anti-CD20 therapies (i.e., rituximab), bortezomib and splenectomy have been used over the years to treat AMR as well as to prevent AMR in high-risk sensitized kidney transplant recipients. Eculizumab and ravulizumab are monoclonal antibodies targeting the C5 protein of the complement pathway and part of the expanding field of anticomplement therapies, which is not limited to kidney transplant recipients, and also includes complement-mediated microangiopathic hemolytic anemia, paroxysmal nocturnal hemoglobinuria, and ANCA-vasculitis. In this narrative review, we summarize the current knowledge concerning the pathophysiological background and use of anti-C5 strategies (eculizumab and ravulizumab) and C1-esterase inhibitor in AMR, either to prevent AMR in high-risk desensitized patients or to treat AMR as first-line or rescue therapy and also to treat de novo thrombotic microangiopathy in kidney transplant recipients.

TMA in Kidney Transplantation

Thrombotic microangiopathy (TMA) is a rare and devastating complication of kidney transplantation, which often leads to graft failure. Posttransplant TMA (PT-TMA) may occur either de novo or as a recurrence of the disease. De novo TMA can be triggered by immunosuppressant drugs, antibody-mediated rejection, viral infections, and ischemia/reperfusion injury in patients with no evidence of the disease before transplantation. Recurrent TMA may occur in the kidney grafts of patients with a history of atypical hemolytic uremic syndrome (aHUS) in the native kidneys. Studies have shown that some patients with aHUS carry genetic abnormalities that affect genes that code for complement regulators (CFH, MCP, CFI) and components (C3 and CFB), whereas in 10% of patients (mostly children), anti-FH autoantibodies have been reported. The incidence of aHUS recurrence is determined by the underlying genetic or acquired complement abnormality. Although treatment of the causative agents is usually the first line of treatment for de novo PT-TMA, this approach might be insufficient. Plasma exchange typically resolves hematologic abnormalities but does not improve kidney function. Targeted complement inhibition is an effective treatment for recurrent TMA and may be effective in de novo PT-TMA as well, but it is necessary to establish which patients can benefit from different therapeutic options and when and how these can be applied.

Caveolin-1 in situ expression in glomerular and peritubular capillaries as a marker of ultrastructural progression and severity of renal thrombotic microangiopathy

BACKGROUND

Thrombotic microangiopathy is a severe and potentially life-threatening condition inducing severe endothelial injury in many organs, particularly native and transplanted kidneys. Current pathological studies by our group have identified the use of Caveolin-1 immunohistochemistry as a potential marker of endothelial damage and progression degree of thrombotic microangiopathy. The aim of the present work was to evaluate Caveolin-1 as a marker of severity in thrombotic microangiopathy kidney disease, according to the ultrastructural progression of the disease evaluated by transmission electron microscopy.

MATERIALS AND METHODS

Twenty-nine patients (17 non-transplanted and 12 transplanted) were retrospectively selected, biopsied for suspected or histologically-confirmed thrombotic microangiopathy. Transmission electron microscopy was performed in all cases, and an ultrastructural score of thrombotic microangiopathy-related glomerular disease was assessed (from 0 to 3+). Immunohistochemistry for Caveolin-1 was automatically performed.

RESULTS

The mean percentage of Caveolin-1-positive glomerular capillaries was 53.2 ± 40.6% and 28.0 ± 42.8% in the active thrombotic microangiopathy versus previous thrombotic microangiopathy cases (p = 0.085), considering both native and transplanted kidneys. The presence of progressive disease correlated with diffuse Caveolin-1 immunoreactivity (p = 0.031), and ultrastructural score correlated with glomerular Caveolin-1 positivity, progressively increasing from 22.5% of the Score 0 group to 95.5% of the Score 3 group (p = 0.036).

DISCUSSION

Caveolin-1 proved to be a very useful marker of early endothelial damage in the course of thrombotic microangiopathy for both native and transplanted kidneys, therefore worth considering in routine practice. Diffuse glomerular Caveolin-1 immunoreactivity correlates with the severity of the thrombotic disease and it can appear very early, even before ultrastructurally evident endothelial damage.

Thrombotic microangiopathies after kidney transplantation in modern era: nosology based on chronology

BACKGROUND

Thrombotic microangiopathies (TMAs) are rare but can be severe in kidney transplant. recipients (KTR).

METHODS

We analysed the epidemiology of adjudicated TMA in consecutive KTR during the. 2009-2021 period.

RESULTS

TMA was found in 77/1644 (4.7%) KTR. Early TMA (n = 24/77 (31.2%); 1.5% of all KTR) occurred during the first two weeks ((median, IQR) 3 [1-8] days). Triggers included acute antibody-mediated rejection (ABMR, n = 4) and bacterial infections (n = 6). Graft survival (GS) was 100% and recurrence rate (RR) was 8%. Unexpected TMA (n = 31/77 (40.2%); 1.5/1000 patient-years) occurred anytime during follow-up (3.0 (0.5-6.2) years). Triggers included infections (EBV/CMV: n = 10; bacterial: n = 6) and chronic active ABMR (n = 5). GS was 81% and RR was 16%. Graft-failure associated TMA (n = 22/77 (28.6%); 2.2% of graft losses) occurred after 8.8 (4.9-15.5) years). Triggers included acute (n = 4) or chronic active (n = 14) ABMR, infections (viral: n = 6; bacterial: n = 5) and cancer (n = 6). 15 patients underwent transplantectomy. RR was 27%. Atypical (n = 6) and typical (n = 2) haemolytic and uremic syndrome, and isolated CNI toxicity (n = 4) were rare. Two-third of biopsies presented TMA features.

CONCLUSIONS

TMA are mostly due to ABMR and infections; causes of TMA are frequently combined. Management often is heterogenous. Our nosology based on TMA timing identifies situations with distinct incidence, causes and prognosis.

Renal Thrombotic Microangiopathy: A Review

Thrombotic microangiopathy (TMA), a pathological lesion observed in a wide spectrum of diseases, is triggered by endothelial injury and/or dysfunction. Although TMA lesions are often accompanied by clinical features of microangiopathic hemolytic anemia, thrombocytopenia, and ischemic end-organ injury, renal-limited forms of TMA are not infrequently encountered in clinical practice. The presence of renal-limited manifestations can be diagnostically challenging, often delaying the initiation of targeted therapy. Prompt investigation and empirical treatment of TMA is warranted to reduce associated morbidity and mortality. Major advances have been made with respect to the pathophysiology of primary TMA entities, with the subsequent development of novel diagnostic tools and lifesaving therapies for diseases like thrombotic thrombocytopenic purpura and complement-mediated TMA. This article will review the clinical presentation and pathologic hallmarks of TMA involving the kidney, and the disease-specific mechanisms that contribute to the endothelial injury that characterizes TMA lesions. Diagnostic approach and both empirical and disease-specific treatment strategies will be discussed, along with the potential role for emerging targeted disease-specific therapies.

Management of drug-induced neutropenia, thrombocytopenia, and anaemia after solid organ transplantation: A comprehensive review

WHAT IS KNOWN AND OBJECTIVE

Advances in the development of more effective immunosuppressive drugs have increased graft survival and drug induced adverse effects. Haematological complications including neutropenia, thrombocytopenia, and anaemia are common side effects that affect the grafts' and patients' outcomes. Several studies have stated the important role of various medications in haematological complications after transplantation. They have reported the incidence and different mechanisms of drug induced cytopenia, as well as an overview of possible treatment modalities. However, there is no comprehensive protocol for the management of these complications following transplantation. This narrative review was performed to develop a comprehensive practical approach for management of drug induced haematological complications following solid organ transplantation.

METHOD

PubMed, Embase, Cochrane library, Web of Science, and Google scholar databases were searched without time limitations until March, 2021. In addition, some valid drug information data bases (Uptodate and Micromedex) were searched for detailed information until October, 2021.

RESULTS AND DISCUSSION

Several immunosuppressive and antimicrobial medications may induce neutropenia, thrombocytopenia or anaemia following transplantation. Most of these agents cause dose-related cytopenia, which resolves with dose reduction or drug withdrawal. However, any change in medications may result in negative consequences such as severe infections, bleeding, cardiovascular complications, acute allograft rejection, and graft or patient loss. Thus, cautious evaluation of the patient's condition and the pharmacological properties of the culprit medication are required.

WHAT IS NEW AND CONCLUSION

Three algorithms are presented to guide healthcare providers in the stepwise management of drug-induced neutropenia, thrombocytopenia, and anaemia after solid organ transplantation.

De-novo-thrombotische Mikroangiopathie (TMA) nach inkompatibler AB0-Nierentransplantation

Anamnese Wir berichten über einen 57-jährigen Patienten, der in unserer Klinik zur geplanten AB0-inkompatiblen Lebendnierentransplantation aufgenommen wurde.

Untersuchungen und Diagnose An Tag 3 post operationem bildeten sich laborchemisch eindeutige Hinweise für eine Denovo-TMA aus. Die renale Entgiftung stagnierte bei initialem regelrechtem Verlauf.

Therapie und Verlauf Durch den Einsatz von Eculizumab 900 mg an d3 und d10 post operationem konnten wir die TMA mit einem anhaltenden Erfolg unterbinden.

Folgerung Zu diskutieren ist, ob ein frühzeitiger Einsatz von Eculizumab bei V. a. De-novo-TMA ein sicherer Weg ist, eine Transplantatdysfunktion zu unterbinden und somit die in der Literatur beschriebene schlechte Prognose für Transplantat und Empfänger zu verbessern.

Primary Hyperaldosteronism: A Rare Cause of Malignant Hypertension with Thrombotic Microangiopathy in a Kidney Transplant Recipient

Thrombotic microangiopathy (TMA) is a rare disease that presents with haemolysis and organ damage. The kidney is one of the main affected organs, and TMA is associated with serious complications and increased mortality. In transplanted patients, TMA is even less common and has a variety of possible causes, including thrombotic thrombocytopenic purpura (TTP) and haemolytic-uremic syndrome (HUS), infections, drugs, autoimmune disease, tumours, and malignant hypertension. Transplant-related causes, such as antibody-mediated rejection, calcineurin inhibitors, and viral infections, need to be considered as well. The authors report a rare case of TMA in a kidney transplant recipient, whose investigation revealed malignant hypertension secondary to primary hyperaldosteronism.

Thrombotic microangiopathy with renal injury: an approach for the general physician

Thrombotic microangiopathy with renal dysfunction is a haematological and renal emergency warranting urgent diagnosis and intervention. As the potential underlying causes may be complex, assessment and management can be challenging for treating clinicians, and a timely and collaborative approach between general physicians, haematologists and nephrologists may be extremely helpful in order to optimise clinical outcomes. This paper will aim to build an understanding of different potential presentations of thrombotic microangiopathies and provide a practical framework for diagnosis and management, using a case-based discussion format, for acute and general physicians. Some aspects of subsequent specialist management are also discussed.

Calcineurin Inhibitor Toxicity in Solid Organ Transplantation

Calcineurin inhibitors (CNIs) have a substantial role in maintaining immunosuppression after solid organ transplantation (SOT). These drugs have a narrow therapeutic window, and individual doses and drug treatment monitoring are necessary. Still, a substantial proportion of patients suffer from short- or long-term calcineurin inhibitor toxicity (CNT), including kidney function impairment, hypertension, neurotoxicity, and metabolic disturbances. The authors discuss pathophysiology, clinical presentation, and histological features of CNT, with focus on renal manifestations. Furthermore, we elucidate recent and ongoing attempts to reduce the burden of CNT in SOT including CNI-sparing and CNI-free regimens.

Exploring the role of the complement system, endothelial injury, and microRNAs in thrombotic microangiopathy after kidney transplantation

Objective

We investigated whether the recipient’s complement system function, kidney graft endothelial ultrastructural injury, and microRNA (miRNA) expression before transplantation may be associated with the risk of posttransplant de novo thrombotic microangiopathy (TMA).

Methods

Complement system function assessment, histological and ultrastructural examination of preimplantation and kidney graft biopsies, and microRNA assessment were performed on kidney transplant recipients (KTRs) with de novo TMA.

Results

On the basis of the clinical course, histological findings, and miRNA patterns, the following two de novo TMA phenotypes were observed: a self-limiting disease that was localized to the kidney graft and a systemic disease that progressed to graft failure without timely treatment. Decreased alternative complement pathway activity and ultrastructural endothelial injury before transplantation were confirmed in all five KTRs and four of five KTRs, respectively, but they did not correlate with de novo TMA severity.

Conclusions

Alternative complement pathway abnormalities in KTRs and endothelial ultrastructural injury on preimplantation biopsy might be associated with de novo posttransplant TMA, although they did not predict posttransplant TMA severity (localized vs. systemic). The specific miRNA expression patterns in preimplantation kidney graft biopsies demonstrated a borderline statistically significant difference and might provide more accurate information on posttransplant TMA severity.

Transplant-associated thrombotic microangiopathy and immune haematological complications following intestine-containing organ transplantation: experience from over 100 consecutive cases

Descriptions of passenger lymphocyte syndrome (PLS), immune cytopenias and transplant-associated thrombotic microangiopathy (TA-TMA) after intestine-containing transplants remain scarce. We describe our centre's experience of these complications from 2007 to 2019. Ninety-six patients received 103 transplants. PLS occurred in 9 (9%) patients (median 12 days post-transplant); all due to ABO antibodies. There were 31 minor ABO mismatch transplants. No patient required change in immunosuppression. Immune cytopenias (excluding PLS) occurred in six patients at an incidence of 1·7/100 patient years; three immune haemolysis, one immune thrombocytopenia, one acquired Glanzmann's and one immune neutropenia; 50% occurred with other cytopenias. All cases eventually responded to treatment, with a median of four treatments (range 1-8) and 5/6 were treated with rituximab. One patient with immune haemolysis required bortezomib. Complications were common in patients with immune cytopenias; 4/6 with infection needing intravenous antibiotics and 3/6 with venous thromboembolism. In 3/6 cases, a secondary cause for the immune cytopenia was evident. Switching from tacrolimus to ciclosporin was not necessary. There were five cases of transplant-associated thrombotic microangiopathy (TA-TMA; 1·5/100 patient years) requiring calcineurin inhibitor withdrawal; two cases associated with acute rejection. Two cases were managed with plasma exchange, one with plasma infusions and one with eculizumab. Further research in this patient group is required.

[De novo thombotic microangiopathy (TMA) after incompatible AB0 renal transplantation]

HISTORY

We report a 57-year-old patient admitted to our hospital for planned AB0-incompatible living kidney transplantation.

FINDINGS AND DIAGNOSIS

On day 3 post operationem, clear laboratory evidence of de novo TMA developed. Renal detoxification stagnated with initial regular course.

THERAPY AND COURSE

By using eculizumab 900 mg on d3 and d10 post operationem, we were able to suppress TMA with a sustained success.

CONCLUSION

It has to be discussed whether an early use of eculizumab in cases of suspected de novo TMA is a safe way to prevent graft dysfunction and thus to improve the poor prognosis for graft and recipient described in the literature.

Thrombotic Microangiopathy After Kidney Transplantation: An Underdiagnosed and Potentially Reversible Entity

Thrombotic microangiopathy is a rare but serious complication that affects kidney transplant recipients. It appears in 0.8–14% of transplanted patients and negatively affects graft and patient survival. It can appear in a systemic form, with hemolytic microangiopathic anemia, thrombocytopenia, and renal failure, or in a localized form, with progressive renal failure, proteinuria, or arterial hypertension. Post-transplant thrombotic microangiopathy is classified as recurrent atypical hemolytic uremic syndrome or de novo thrombotic microangiopathy. De novo thrombotic microangiopathy accounts for the majority of cases. Distinguishing between the 2 conditions can be difficult, given there is an overlap between them. Complement overactivation is the cornerstone of all post-transplant thrombotic microangiopathies, and has been demonstrated in the context of organ procurement, ischemia-reperfusion phenomena, immunosuppressive drugs, antibody-mediated rejection, viral infections, and post-transplant relapse of antiphospholipid antibody syndrome. Although treatment of the causative agents is usually the first line of treatment, this approach might not be sufficient. Plasma exchange typically resolves hematologic abnormalities but does not improve renal function. Complement blockade with eculizumab has been shown to be an effective therapy in post-transplant thrombotic microangiopathy, but it is necessary to define which patients can benefit from this therapy and when and how eculizumab should be used.

Clinical profile and outcomes of De novo posttransplant thrombotic microangiopathy

Thrombotic microangiopathy (TMA) after kidney transplant is rather uncommon but an important reversible cause of graft loss. This retrospective study of biopsy-proven posttransplant TMA was done to identify the important etiological factors, clinical features, and outcomes of post transplant TMA in a tertiary care referral hospital in northern India. This retrospective study was conducted among all renal transplant recipients who presented with graft dysfunction between 1989 and 2015. All the cases were looked for their etiology, clinical course, treatment modalities, and renal outcomes. The study was conducted in accord with prevailing ethical principles and reviewed by our own institutional review board. Seventeen patients out of 2000 (0.008%) transplants done during the study period had posttransplant TMA, out of which all the patients had de novo TMA, and the median time of presentation after transplantation was four months. Systemic TMA was noted in only four patients. Biopsy revealed associated rejection in five patients and associated calcineurin inhibitor (CNI) toxicity in 12 patients. Patients with TMA due to CNI toxicity were managed with CNI reduction or switching to alternate CNI or mammalian target of rapamycin inhibitors. In addition, antithymocyte globulin and plasma exchange were used in rejection-associated TMA. While four out of 12 patients (33%) in CNI-related TMA developed end-stage renal disease (ESRD), all patients in rejection-associated TMA developed ESRD. The overall one-year graft survival was 47%, whereas five- and 10-year survival was 35%. There was no significant difference in graft survival between localized and systemic TMAs (P = 0.4). Posttransplant TMA should be suspected even if there are no systemic features of hemolysis and early graft biopsy and prompt action is needed. The occurrence of TMA in the setting of rejection is associated with grave prognosis.

Eculizumab interruption in atypical hemolytic uremic syndrome due to shortage: analysis of a Brazilian cohort

BACKGROUND

The risk of eculizumab therapy discontinuation in patients with atypical hemolytic uremic syndrome (aHUS) is unclear. The main objective of this study was to analyze the risk of aHUS relapse after eculizumab interruption due to drug shortage in Brazil.

METHODS

We screened all the registered dialysis centers in Brazil (n = 800), willing to participate in the aHUS Brazilian shortage cohort, through electronic mail and formal invitation by the Brazilian Society of Nephrology. We included patients with aHUS whose eculizumab therapy underwent unplanned discontinuation for at least 30 days between January 1st, 2016 and December 31st, 2019 during the maintenance phase of treatment. Relapse was defined by the development of thrombocytopenia, hemolytic anemia, acute kidney injury or thrombotic microangiopathy (TMA) in a kidney biopsy.

RESULTS

We analyzed 25 episodes of exposure to risk of relapse, from 24 patients. Median age was 33 (6-53) years, 18 (72%) were female, 9 (36%) had a functioning renal graft, 5 (20%) were undergoing dialysis. CFH variant was found in 8 (32%) episodes. There were 11 relapses. The risk of relapse was 34%, 44.5% and 58% at 114, 150 and 397 days, respectively. No baseline variable was related to relapse in Cox multivariate analysis, including CFH variant.

CONCLUSIONS

In this study, the cumulative incidence of aHUS relapse at 397 days was 58% after eculizumab interruption. The presence of complement variant does not seem to be associated with a higher relapse rate. The eculizumab interruption was deemed not safe, considering that the rate of relapse was high.

Use of Eculizumab in Transplant-Associated Thrombotic Microangiopathy in a Patient With Polycystic Kidney Disease Immediately Post-Kidney Transplant: A Case Report

Transplant-associated thrombotic microangiopathy (TMA) in the post-organ transplantation setting occurs from a number of potential inciting factors, such as the use of calcineurin inhibitors, ischemic injury, infections, or antibody-mediated rejection leading to unchecked complement activation and end-organ damage. Delayed recognition of this condition can result in allograft loss. In this case description, we describe the first case of de novo TMA in a patient with polycystic kidney disease that occurred immediately after kidney transplantation. The diagnosis was made promptly on the basis of clinical and laboratory characteristics by a multidisciplinary team and confirmed through kidney biopsy, which showed acute TMA. The patient was successfully managed by replacing tacrolimus with belatacept, which targets cytotoxic T lymphocyte antigen 4, and use of eculizumab, a C5 inhibitor. Eculizumab treatment was discontinued after 3 months of complement inhibition on the patient's request, and relapse of TMA has not been encountered after more than 1 year of follow-up.

Thrombotic Thrombocytopenic Purpura: Revisiting a Miss and an Inevitable Consequence

Thrombotic thrombocytopenic purpura (TTP) is typically characterized by the symptomatic pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, neurologic abnormalities, and renal failure. Atypical TTP is the diagnosis used to describe the subset of patients with TTP who present with symptoms that deviate from the classic pentad. We report a case an 86-year-old woman who presented to the emergency department complaining of chest pain for one day. She was reportedly on antibiotics for sinus infection. Physical examination revealed multiple bilateral superficial hematomas, predominantly on her extremities. On admission, her lab values were as follows: platelet count of 6,000/cubic millimeter, hemoglobin of 10.4 grams/deciliter, leukocyte count of 5100 cells/cubic millimeter, total bilirubin of 2.3 milligrams/deciliter, and troponin-I of 5.190 nanograms/milliliter. Peripheral blood smear was normal and did not reveal any schistocytes. The patient was admitted to the intensive care unit with a diagnosis of a non-ST-elevation myocardial infarction and a presumed diagnosis of immune thrombocytopenic purpura from antibiotic use. She was treated with intravenous solumedrol and a high-intensity statin. On the third day of her admission, the patient's mental functioning deteriorated and was intubated to protect her airway. A second peripheral smear revealed schistocytes, and subsequent laboratory studies supported the diagnosis of TTP. Plasma exchange therapy was planned. However, the patient succumbed to cardiac arrest before it could be initiated. The diagnosis was later confirmed with an ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) assay.  This case serves as an example of one of the many ways in which TTP can present, and emphasizes the importance of considering TTP as a differential diagnosis.

vWFpp/ADAMTS13 ratio is a useful marker of postliver transplantation thrombotic microangiopathy: A pediatric case report

vWFpp/ADAMTS13 ratio should be further studied as a useful marker for diagnosis of thrombotic microangiopathy postliver transplantation. Immunosuppressive regimen modification and plasma supplementation can lead to recovery.

Thrombotic microangiopathy in a renal allograft: Single-center five-year experience

Thrombotic microangiopathy (TMA) is devastating for renal transplantation (RT) causing graft/ patient loss. We present 5-year experience of TMA in RT in retrospective study of indicated renal allograft biopsies with TMA. Patient-donor demographics and associated histological findings with respect to transplants under tolerance induction protocol (Group 1) were compared with patients transplanted under triple immunosuppression (Group 2). Statistical analysis was performed using IBM SPSS Statistics version 20. Sixty-one (4.1%) of 1520 biopsies [Group 1:17 (1.9%)/882, Group 2:44 (6.9%)/638] revealed TMA. Tacrolimus trough levels were normal. There was no evidence of systemic involvement in any patient. Mean age was 36.8 years with 70.6% males, HLA-match, 2.6/6, and the most common original disease unknown (41.2%) in Group 1, and 35.9 years with 86.4% males, HLA-match, 2.1/6, and the most common original disease unknown (50%) in Group 2. Biopsies were performed at mean 5.1-year posttransplant in Group 1 and 2.3 years in Group 2. Acute TMA constituted 47% Group 1 and 43.2% Group 2 biopsies; of these, antibody-mediated rejections were observed in 58.8%, T-cell mediated rejections in 11.8%, tacrolimus toxicity in 76.5%, and other findings in 35.3% Group 1; and 61.4%, 25%, 50%, and 18.2%, respectively, in Group 2 biopsies. Higher rejection activity scores were more in Group 2. Postbiopsy 1- and 5- year patient survival was 94.1%, 86.9% in Group 1 and 92.1%, 88.3% in Group 2; 1- and 4-year graft survival was 52.9%, 15.9% in Group 1 and 20.3%, 5.4% in Group 2. TMA was poor prognosticator for RT, especially under triple immunosuppression. Antibody- mediated rejection and tacrolimus toxicity were more prone to TMA.

Consensus regarding diagnosis and management of atypical hemolytic uremic syndrome

Thrombotic microangiopathy (TMA) is defined by specific clinical characteristics, including microangiopathic hemolytic anemia, thrombocytopenia, and pathologic evidence of endothelial cell damage, as well as the resulting ischemic end-organ injuries. A variety of clinical scenarios have features of TMA, including infection, pregnancy, malignancy, autoimmune disease, and medications. These overlapping manifestations hamper differential diagnosis of the underlying pathogenesis, despite recent advances in understanding the mechanisms of several types of TMA syndrome. Atypical hemolytic uremic syndrome (aHUS) is caused by a genetic or acquired defect in regulation of the alternative complement pathway. It is important to consider the possibility of aHUS in all patients who exhibit TMA with triggering conditions because of the incomplete genetic penetrance of aHUS. Therapeutic strategies for aHUS are based on functional restoration of the complement system. Eculizumab, a monoclonal antibody against the terminal complement component 5 inhibitor, yields good outcomes that include prevention of organ damage and premature death. However, there remain unresolved challenges in terms of treatment duration, cost, and infectious complications. A consensus regarding diagnosis and management of TMA syndrome would enhance understanding of the disease and enable treatment decision-making.

Diagnostic Testing for Differential Diagnosis in Thrombotic Microangiopathies

Thrombotic microangiopathies (TMAs) are multiple disease entities with different etiopathogeneses, characterized by thrombocytopenia, microangiopathic hemolytic anemia (MAHA) with schistocytosis, variable symptoms including fever, and multi-organ failure such as mild renal impairment and neurological deficits. The two paradigms of TMAs are represented on one hand by acquired thrombotic thrombocytopenic purpura (TTP) and on the other by hemolytic uremic syndrome (HUS). The differential diagnosis between these two paradigmatic forms of TMA is based on the presence of either frank renal failure in HUS or a severe deficiency (<10%) of the zinc-protease ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) in TTP. ADAMTS13 is an enzyme involved in the proteolytic processing of von Willebrand factor (vWF), and its deficiency results in formation of high-molecular-weight vWF-rich microthrombi in the environment of the microvasculature. The presence of these ultra-large vWF multimers in the microcirculation can recruit platelets, promoting multi-organ ischemic lesions. The presence of ADAMTS13 activity at >10% could rule out the presence of a TTP form. However, it is often difficult to differentiate either a TTP or HUS clinical scenario presenting with typical symptoms of TMA. There are in fact several additional diagnoses that should be considered in patients with ADAMTS13 activity of >10%. Widespread inflammation with endothelial damage and adverse reactions to drugs play a central role in the pathogenesis of several forms of TMA, and in these cases, the differential diagnosis should be directed at the underlying disease. Hence, a correct etiologic diagnosis of TMA should involve a critical illness, cancer-associated TMA, drug-induced TMA, and hematopoietic transplant-associated TMA. A complete assessment of all the possible etiologies for TMA symptoms, including acquired or congenital TTP, will allow for a more accurate diagnosis and application of a more appropriate treatment.

Analysis of the prevalence of systemic de novo thrombotic microangiopathy after ABO-incompatible kidney transplantation and the associated risk factors

OBJECTIVES

To analyze the prevalence of systemic de novo thrombotic microangiopathy in ABO-incompatible kidney transplantation and risk factors associated with this condition.

METHODS

A total of 201 patients who received living-donor kidney transplantation (114 patients with ABO-identical kidney transplantation and 87 patients with ABO-incompatible kidney transplantation) were retrospectively analyzed. Systemic de novo thrombotic microangiopathy was diagnosed clinically according to the presence of thrombocytopenia with microangiopathic hemolytic anemia and pathological findings of thrombotic microangiopathy. Anti-A and anti-B antibodies were purified from human plasma, and these antibodies' bindings to human kidney were investigated in vitro.

RESULTS

ABO-incompatible kidney transplantation was a significant risk factor of systemic de novo thrombotic microangiopathy (odds ratio 55.9, 95% CI 1.8-8.9, P < 0.001) after transplantation. Multivariate logistic regression analysis showed that non-use of mycophenolate mofetil, pretreatment immunoglobulin G antibody titer ≥64-fold and pretransplant immunoglobulin M antibody titer ≥16-fold were significant risk factors for systemic de novo thrombotic microangiopathy in ABO-incompatible kidney transplantation. Microvascular inflammation of 1-h post-transplant biopsy could be observed more frequently in thrombotic microangiopathy patients than in non-thrombotic microangiopathy patients. Anti-A and anti-B antibodies purified from human plasma showed a strong in vitro reaction against human kidney when the antibody titer was ≥16-fold.

CONCLUSIONS

Antibody titer should be decreased to ≤16-fold until the day of ABO-incompatible kidney transplantation by desensitization therapy including mycophenolate mofetil. The 1-h biopsy results might help to diagnose systemic de novo thrombotic microangiopathy.

Evaluation of the Renal Transplant Recipient in the Emergency Department

Renal transplants are becoming more and more frequent in the United States and worldwide. Studies demonstrate that these patients inevitably end up visiting an emergency department. In addition to typical medical and surgical problems encountered in the general population, this group of patients has unique problems arising from their immunocompromised state and also due to side effects of the medications required. This article discusses these risks and management decisions that the emergency department physician should be aware of in order to prevent adverse outcomes for the patient and transplanted kidney.

Antiphospholipid Syndrome Nephropathy and Other Thrombotic Microangiopathies Among Patients With Systemic Lupus Erythematosus

Antiphospholipid syndrome (APS) and other causes of thrombotic microangiopathy (TMA) negatively impact the renal outcomes of patients with systemic lupus erythematosus (SLE) and lupus nephritis. Here we review the diagnosis and management of occlusive renal vascular lesions due to APS and other TMAs, with a focus on patients with SLE and lupus nephritis. The presence of a thrombotic event, unexplained hypertension, thrombocytopenia, or hemolytic anemia should prompt consideration for TMA syndromes. The differential diagnosis of a TMA in a patient with SLE includes APS, thrombocytopenic purpura, complement-mediated or infection-associated hemolytic uremic syndrome, drug-mediated TMA (particularly due to calcineurin inhibitor toxicity), and malignant hypertension. Treatment of APS with a documented thrombotic event focuses on anticoagulation to reduce the risk for further thrombotic events. Treatment of classic presentations of thrombocytopenic purpura and hemolytic uremic syndrome in the SLE population is the same as in patients without SLE. Treatment of APS nephropathy or TMA when it is diagnosed by biopsy with concomitant lupus nephritis presents a challenge to clinicians because there is no clear standard of care. Small and retrospective studies suggest potential benefit of complement inhibition, mammalian target of rapamycin (mTOR) inhibition, B cell depleting therapy, and plasma exchange therapy for patients with lupus nephritis and TMA, and prospective investigation of these therapies should be a research priority.